This invention relates generally to the field of surgical instruments and more particularly is directed to a hand-held surgical instrument used for describing an occular incision particularly suited for cataract surgery in order to obtain access to the cataract lens.
A cataract lens, or one which has become partially or wholly opaque, sometimes requires removal from the eye depending upon a variety of circumstances which are taken into consideration by the ophthalmic surgeon. Once a decision has been made to remove the cataract lens a variety of techniques have been developed and are available depending upon the particular condition of the lens material itself. Two such known techniques are: "extracapsular cataract extraction" and "intracapsular cataract extraction".
Ultrasonic cataract remova is one form of extracapsular extraction. This involves the insertion of an ultrasonic probe into the lens material and activating the probe for emulsifying the lens. The emulsified material can then be aspirated by a variety of electronic and hydraulic equipment. Examples of such techniques can be seen in U.S. Pat. Nos. 3,589,363 and 3,857,387.
A variety of vibrating tools, suction devices, hydraulic implements, and electronic controls have been developed and are required for cataract removal when using the ultrasonic removal techniques.
Because, however, of the delicacy of the positioning of the probe, the use of complex and costly electronic or hydraulic equipment, possibilities of complications in post operative care, the degree of skill required to ensure complete fragmentation of the lens material and subsequent aspiration of the emulsified material, and a variety of other reasons, the ultrasonic cataract removal techniques have not become as widely used as originally anticipated.
Additionally, the use of the ultrasonic technique must be limited to removal of cataract lenses which are either congenital, up to approximately the age of 20 or to those in which the consistency of the lens is still semifluidic. However, when the lens material becomes hardened ultrasonic emulsification and subsequent aspiration is difficult if not impossible. In such situations, the more traditional technique of intracapsular extraction is preferred. Furthermore, it is believed that intracapsular cataract extractions involve less possibility of post operative complications and provide greater opportunity for ensuring complete removal of the cataract lens element.
Therefore, removal of cataract lenses by the intracapsular technique is still a popular if not the preferred method amongst ophthalmic surgeons. In the intracapsular extraction technique, a conjunctive flap is first formed by making an incision in the conjunctiva so that it may be moved back to expose the sclera of the eye at the corneal border.
In order to obtain access to the cataract lens, which is located behind the cornea, an incision is then formed extending approximately between 140.degree. and 180.degree. around the cornear in the limbus area and desirably spaced 0 to 2 mm from the periphery of the cornea. The various types of locations of this incision is described at some length in Cataract Surgery And Its Complications by Norman S. Jaffe, the C. V. Mosby Company St. Louis 1972. One of the more desirable types of incisions is a multiplane incision in which a first cut (in a first plane) extends only partially through the thickness of the eye. This partial thickness incision is commonly referred to as a "cataract groove". Second, and sometimes third incisions, in second and third planes, are then made to enter the anterior chamber for access to the lens. The first incision or groove typically extends to a depth of approximately one-half the thickness of the wall of the eye globe by use of a rounded scalpel blade, razor blade or other instrument, either perpendicular to the wall of the globe or at an angle beveled to the surface of the globe. The initial incision or groove may be enlarged with either a scissor, keratome or other blade implement. Once the entire incision is completed, the cornea may be lifted or retracted to gain access to the anterior chamber. The cataract lens may then be extracted through the use of any number of techniques, such as cryo extraction (the formation of an ice ball in contact with the lens capsule formed at the tip of a cryo probe) or by gripping the lens by a forceps device. The techniques for lens extraction are described more fully in the above mentioned Cataract Surgery And Its Complications.
The groove, or multiplane type of incision, has a number of advantages over an incision which lies in a single plane and extends through the full thickness of the eye into the anterior chamber. First, after the groove is formed, radially arranged sutures may be preplaced across the groove before the entire incision is completed so as to insure exact lateral realignment after the operation. Preplaced sutures also allows the surgeon the option of quickly closing the wound at any time during the procedure should circumstances demand that the wound be so closed. Secondly, a multiplane incision provides control over depth realignment, whereas a single plane incision involves possible difficulties in exact depth repositioning of the opposing sides of the incision with respect to each other.
Because the groove (first incision) has heretofore been typically formed by free hand, no two grooves can ever be expected to be exactly the same. Accordingly, results and post operative effects cannot be accurately anticipated. In addition, because the free hand groove can never be perfectly semi-circular, the placement of sutures in often a difficult procedure.
In addition to the lack of uniformity created by free hand describing of the groove, the surgeon often has difficulty in completing the full 140.degree.-180.degree. incision since the cutting edge is usually supported in a holder which is gripped by the surgeon in one hand, while he stabilizes the globe of the eye through the use of a fixator or forceps element carried in the other hand. Accordingly, it is necessary for the surgeon to both rotate the globe using the fixator in one hand while rotating the position of the cutting edge with the other hand, often finding himself in an awkward position and unable to complete the groove in a single sweeping motion. This frequently results in a groove which is either not smooth or which may not be positioned in the desired location.
It should be noted, that while the groove or multiplane incision is desired, the present invention may be used with satisfactory results to accomplish either a groove or a full thickness incision.
One recent attempt to overcome some of the foregoing disadvantages of forming a groove free hand is described in an article in the 1975 Fall Issue (Volume 6, No. 3) of the periodical Ophthalmic Surgery, by James T. Pattern entitled "Groove Maker for Cataract Surgery". The instrument described in this article was formed by modifying a corneal trephine. The diameter of the cutting edge was split to form a curved cutting surface having an arc of approximately 100.degree. and a radius of curvature of 6 mm. The curved cutting surface is then applied to the desired position on the limbus and then twisted back and forth by free hand movement of the surgeon to complete the desired 140.degree.-180.degree. groove. While the use of this instrument would appear to be an advance in the formation of the cataract groove it still requires a certain degree of free hand movement and judgment in the placement of the cutting surface.
It is accordingly a general object of the present invention to provide an instrument for forming a cataract groove which overcomes all of the disadvantages of the prior art.
It is a further and more specific object of the present invention to provide and ophthalmic surgical instrument used in surgery for removing cataract lenses from the eye be enabling the surgeon to describe an incision concentric with the cornea of predetermined radius and uniform curvature, depth and angle with absolute accuracy and consistency for each operation performed.
It is yet another object of the present invention to provide an improved means for forming an incision in the wall of the eye to permit access to the anterior chamber for removal of cataract lenses.
A still further object of the present invention is to provide an instrument having means for fixing the globe of the eye and means to describe an incision with respect to the periphery of the cornea determined by the position of the fixating element.
The above objects, features and advantages, along with other objects, features and advantages of the present invention will become more apparent from the detailed description of the invention in conjunction with the accompanying drawings to be described more fully hereinafter.